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source: branches/Async/HeuristicLab.Encodings.RealVectorEncoding/3.3/Crossovers/UniformAllPositionsArithmeticCrossover.cs @ 13985

Last change on this file since 13985 was 12012, checked in by ascheibe, 10 years ago

#2212 merged r12008, r12009, r12010 back into trunk

File size: 5.8 KB
Line 
1#region License Information
2/* HeuristicLab
3 * Copyright (C) 2002-2015 Heuristic and Evolutionary Algorithms Laboratory (HEAL)
4 *
5 * This file is part of HeuristicLab.
6 *
7 * HeuristicLab is free software: you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation, either version 3 of the License, or
10 * (at your option) any later version.
11 *
12 * HeuristicLab is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with HeuristicLab. If not, see <http://www.gnu.org/licenses/>.
19 */
20#endregion
21
22using System;
23using HeuristicLab.Common;
24using HeuristicLab.Core;
25using HeuristicLab.Data;
26using HeuristicLab.Parameters;
27using HeuristicLab.Persistence.Default.CompositeSerializers.Storable;
28
29namespace HeuristicLab.Encodings.RealVectorEncoding {
30  /// <summary>
31  /// The uniform all positions arithmetic crossover constructs an offspring by calculating x = alpha * p1 + (1-alpha) * p2 for every position x in the vector.
32  /// </summary>
33  /// <remarks>
34  /// By setting alpha = 0.5 it is the same as the <see cref="AverageCrossover"/>, but only on two parents.
35  /// It is implemented as described in Michalewicz, Z. 1999. Genetic Algorithms + Data Structures = Evolution Programs. Third, Revised and Extended Edition, Spring-Verlag Berlin Heidelberg.
36  /// </remarks>
37  [Item("UniformAllPositionsArithmeticCrossover", "The uniform all positions arithmetic crossover constructs an offspring by calculating x = alpha * p1 + (1-alpha) * p2 for every position x in the vector. Note that for alpha = 0.5 it is the same as the AverageCrossover (except that the AverageCrossover is defined for more than 2 parents). It is implemented as described in Michalewicz, Z. 1999. Genetic Algorithms + Data Structures = Evolution Programs. Third, Revised and Extended Edition, Spring-Verlag Berlin Heidelberg.")]
38  [StorableClass]
39  public class UniformAllPositionsArithmeticCrossover : RealVectorCrossover {
40    /// <summary>
41    /// The alpha parameter needs to be in the interval [0;1] and specifies how close the resulting offspring should be either to parent1 (alpha -> 0) or parent2 (alpha -> 1).
42    /// </summary>
43    public ValueLookupParameter<DoubleValue> AlphaParameter {
44      get { return (ValueLookupParameter<DoubleValue>)Parameters["Alpha"]; }
45    }
46
47    [StorableConstructor]
48    protected UniformAllPositionsArithmeticCrossover(bool deserializing) : base(deserializing) { }
49    protected UniformAllPositionsArithmeticCrossover(UniformAllPositionsArithmeticCrossover original, Cloner cloner) : base(original, cloner) { }
50    /// <summary>
51    /// Initializes a new instance with one parameter (<c>Alpha</c>).
52    /// </summary>
53    public UniformAllPositionsArithmeticCrossover()
54      : base() {
55      Parameters.Add(new ValueLookupParameter<DoubleValue>("Alpha", "The alpha value in the range [0;1]", new DoubleValue(0.33)));
56    }
57
58    public override IDeepCloneable Clone(Cloner cloner) {
59      return new UniformAllPositionsArithmeticCrossover(this, cloner);
60    }
61
62    /// <summary>
63    /// Performs the arithmetic crossover on all positions by calculating x = alpha * p1 + (1 - alpha) * p2.
64    /// </summary>
65    /// <exception cref="ArgumentException">Thrown when the parent vectors are of different length or alpha is outside the range [0;1].</exception>
66    /// <param name="random">The random number generator.</param>
67    /// <param name="parent1">The first parent vector.</param>
68    /// <param name="parent2">The second parent vector.</param>
69    /// <param name="alpha">The alpha parameter (<see cref="AlphaParameter"/>).</param>
70    /// <returns>The vector resulting from the crossover.</returns>
71    public static RealVector Apply(IRandom random, RealVector parent1, RealVector parent2, DoubleValue alpha) {
72      int length = parent1.Length;
73      if (length != parent2.Length) throw new ArgumentException("UniformAllPositionsArithmeticCrossover: The parent vectors are of different length.", "parent1");
74      if (alpha.Value < 0 || alpha.Value > 1) throw new ArgumentException("UniformAllPositionsArithmeticCrossover: Parameter alpha must be in the range [0;1]", "alpha");
75      RealVector result = new RealVector(length);
76      for (int i = 0; i < length; i++) {
77        result[i] = alpha.Value * parent1[i] + (1 - alpha.Value) * parent2[i];
78      }
79      return result;
80    }
81
82    /// <summary>
83    /// Checks that there are exactly 2 parents, that the alpha parameter is not null and fowards the call to <see cref="Apply(IRandom, RealVector, DoubleArrrayData, DoubleValue)"/>.
84    /// </summary>
85    /// <exception cref="ArgumentException">Thrown when there are not exactly two parents.</exception>
86    /// <exception cref="InvalidOperationException">Thrown when the alpha parmeter could not be found.</exception>
87    /// <param name="random">The random number generator.</param>
88    /// <param name="parents">The collection of parents (must be of size 2).</param>
89    /// <returns>The vector resulting from the crossover.</returns>
90    protected override RealVector Cross(IRandom random, ItemArray<RealVector> parents) {
91      if (parents.Length != 2) throw new ArgumentException("UniformAllPositionsArithmeticCrossover: There must be exactly two parents.", "parents");
92      if (AlphaParameter.ActualValue == null) throw new InvalidOperationException("UniformAllPositionsArithmeticCrossover: Parameter " + AlphaParameter.ActualName + " could not be found.");
93      return Apply(random, parents[0], parents[1], AlphaParameter.ActualValue);
94    }
95  }
96}
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